[m: ]
从下标为m的元素开始取全部
a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
print(a[1:])
print(a[2:])
运行结果:
[2, 3, 4, 5, 6, 7, 8, 9, 10]
[3, 4, 5, 6, 7, 8, 9, 10]
[ :n]
取到下标为n-1的元素
a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
print(a[:3])
print(a[:9])
运行结果:
[1, 2, 3]
[1, 2, 3, 4, 5, 6, 7, 8, 9]
[m:n]
从下标为m的元素取到下标为n-1的元素
a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
print(a[0:3])
print(a[1:9])
运行结果:
[1, 2, 3]
[2, 3, 4, 5, 6, 7, 8, 9]
[m::n]
后面的n是取元素的间隔,从下标为m的元素开始取,接着是下标为m+n的元素,直到结束
a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
print(a[2::2])
print(a[::-1])
运行结果:
[3, 5, 7, 9]
[10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
注意:
[::-1]可以理解为从无开始,然后取下标为-1的元素,接着是下标为-2的元素,直到结束,这样看起来也就是将元素取反。